Protestant majority predicted to fall sharply

The Protestant majority in Northern Ireland is expected to show a sharp decline when results from this month's census are published. Catholics may already account for more than 46% of the population.

But two factors have left in the balance the crucial question of whether nationalists will overtake unionists: rapid decline in the Catholic birth-rate and the unprecedented impact of immigration.

The arrival of the census once every 10 years always raises sectarian temperatures. In 1971, republicans burnt forms in protest at unionist gerrymandering of the Stormont government. Ten years later the IRA shot dead a census taker in Derry; she was deemed to be an official of the occupying British state. By 1991, Sinn Fein's position had been reversed. Chasing an electoral mandate, republicans became eager to register the rapid growth in numbers of predominantly nationalist-voting Catholics.

Final calculations of the relative size of the Catholic and Protestant populations, however, are complicated by the fact that many respondents decline to state any religious affiliation. By common assumption, the 1991 census suggested Northern Ireland was around 42% Catholic and 58% Protestant. Nearly 300,000 people - 18% of the population - that year declined to state their religion.

Following the last census, some statisticians suggested Catholics could constitute a majority in Northern Ireland by 2025. Sinn Fein has implied the changeover might arrive as early as the census after next, in 2011.

Ian Shuttleworth, a geography lecturer at Queen's University, Belfast, yesterday accepted that projecting forward past trends indicates this year's census on April 29 would result in a narrowing Catholic minority of between 46 to 48%. But immigration into Northern Ireland - the province's population has grown since 1991 by 100,000 to 1.67m - has cast doubt on the reliability of previous trends.

No one knows if the influx is made up predominantly of returning Catholics or Protestants. "The traditionally high Catholic birthrate is also falling faster than the Protestant one," Dr Shuttleworth said.